The International Convention for the Prevention of Pollution from Ships (MARPOL) is a critical global initiative that aims to minimize maritime pollution and protect the world’s oceans and marine ecosystems. Annex VI, officially known as the “Prevention of Air Pollution from Ships,” is a vital component of this convention. Introduced in 1997 and enforced in 2005, Annex VI sets forth stringent regulations and guidelines to limit harmful emissions from ships, specifically targeting the release of sulfur oxides (SOx), nitrogen oxides (NOx), ozone-depleting substances (ODS), and volatile organic compounds (VOCs).
As a response to growing concerns about air pollution, climate change, and the detrimental effects on human health and the environment, Annex VI has been revised and updated several times to reflect technological advancements and the latest scientific understanding. The Energy Efficiency Design Index (EEDI) and the Ship Energy Efficiency Management Plan (SEEMP) are notable additions, aiming to enhance the energy efficiency of ships and reduce greenhouse gas emissions.
Through international cooperation and the diligent efforts of the International Maritime Organization (IMO) and its member states, Annex VI has proven to be a valuable instrument in the fight against air pollution from shipping. The global community’s commitment to this cause has led to cleaner air, healthier ecosystems, and a more sustainable future for the shipping industry.
MARPOL Annex VI
In 1997, a new annex was added to the International Convention for the Prevention of Pollution from Ships (MARPOL). The Prevention of Air Pollution from Ships (Annex VI) regulations seek to minimize airborne emissions from ships (SOx, NOx, ODS, VOC shipboard incineration) and their contribution to local and global air pollution and environmental problems. Annex VI entered into force in 2005, and a revised Annex VI with significantly tightened emissions limits entered into force on 1 July 2010. Here is the list of Regulations in Annex VI , updated by the end of 2022:
| Regulation Number | Title/Description |
| Regulation 1 | General – Definitions, Application, and Exemptions |
| Regulation 2 | Ozone-depleting substances |
| Regulation 3 | Nitrogen oxides (NOx) |
| Regulation 4 | Sulfur oxides (SOx) and particulate matter |
| Regulation 5 | Volatile organic compounds (VOCs) |
| Regulation 6 | Shipboard incineration |
| Regulation 7 | Reception facilities |
| Regulation 8 | Port State control on operational requirements |
| Regulation 9 | Requirements for platforms and drilling rigs |
| Regulation 10 | Requirements for recreational craft |
| Regulation 11 | Energy efficiency for ships |
| Regulation 12 | Onboard monitoring and reporting of energy efficiency |
| Regulation 13 | Nitrogen oxides (NOx) Tier III emission standards |
| Regulation 14 | Reduction of sulfur oxide (SOx) emissions |
| Regulation 15 | Fuel oil quality |
| Regulation 16 | Verification procedures for a MARPOL Annex VI fuel oil sample |
| Regulation 17 | Detection of violations and enforcement of the requirements |
Regulation 1: General – Definitions, Application, and Exemptions
Regulation 1 of MARPOL Annex VI lays the foundation for the rest of the annex by defining key terms, specifying the scope of application, and providing guidance on exemptions. The definitions provided in this regulation include terms such as “ship,” “new ship,” “marine diesel engine,” “gross tonnage,” “ozone-depleting substances,” “volatile organic compounds,” and “emission control areas,” among others.
The regulation applies to all ships, regardless of their size or flag, with specific requirements depending on the type and size of the ship. Some regulations within Annex VI are applicable only to certain ship categories or sizes, and the scope of application is specified accordingly in each regulation.
Exemptions may be granted by the flag state under certain conditions, such as when a ship is engaged in trials for the development of ship emission reduction and control technologies. Temporary exemptions may also be allowed for ships that are not expected to operate in emission control areas for more than a limited period. However, these exemptions must not compromise the overall objectives of Annex VI, and any ship granted an exemption must still take steps to minimize harmful emissions as much as possible.
Regulation 2: Ozone-depleting substances
Regulation 2 of MARPOL Annex VI focuses on minimizing the impact of ships on the ozone layer by prohibiting the deliberate emissions of ozone-depleting substances (ODS) and controlling their use in shipboard equipment. Ozone-depleting substances are chemicals that can cause significant damage to the Earth’s ozone layer, which protects living organisms from harmful ultraviolet (UV) radiation.
This regulation bans the deliberate venting of ODS from refrigeration and air-conditioning systems, fire-extinguishing systems, and other equipment containing such substances. In addition, ships are required to maintain a list of equipment containing ODS and a record book of ODS usage, including the servicing and disposal of equipment containing ODS.
Furthermore, Regulation 2 mandates that new installations of equipment containing ODS are prohibited on all ships. Ships are also required to use only those ODS that comply with the acceptable purity standards set by the regulation. This helps ensure that harmful emissions are minimized and that the shipping industry moves towards more environmentally friendly alternatives.
Regulation 3: Nitrogen oxides (NOx)
Regulation 3 of MARPOL Annex VI aims to reduce the emissions of nitrogen oxides (NOx) from marine diesel engines by establishing specific emission limits based on the engine’s date of installation and its speed. NOx emissions contribute to the formation of smog, acid rain, and the eutrophication of water bodies, which can lead to harmful algal blooms and oxygen-depleted “dead zones.”
To address these concerns, the regulation sets forth three tiers of NOx emission standards for marine diesel engines:
- Tier I: Applies to engines installed on ships constructed on or after January 1, 2000, and prior to January 1, 2011.
- Tier II: Applies to engines installed on ships constructed on or after January 1, 2011.
- Tier III: Applies to engines installed on ships constructed on or after January 1, 2016, when operating in designated NOx Emission Control Areas (NECAs).
These tiers represent progressively stricter emission limits, with Tier III engines required to meet the most stringent standards. The specific emission limits are determined by the engine’s rated speed (in revolutions per minute), with slower engines generally having higher allowable NOx emissions.
Regulation 4: Sulfur oxides (SOx) and particulate matter
Regulation 4 of MARPOL Annex VI targets sulfur oxide (SOx) emissions and particulate matter produced by ships, which can cause respiratory issues, heart disease, and other health problems for humans, as well as contribute to acid rain and the deterioration of ecosystems. This regulation outlines the limits for sulfur content in marine fuels and establishes Emission Control Areas (ECAs) with more stringent standards.
The global cap on the sulfur content of marine fuels was reduced to 0.50% m/m (mass by mass) on January 1, 2020, significantly decreasing the amount of SOx emissions from ships. Prior to this change, the global cap was set at 3.50% m/m. Additionally, within designated ECAs, the sulfur content limit is even lower at 0.10% m/m. This lower limit applies to ships operating in the Baltic Sea, the North Sea, the North American ECA, and the United States Caribbean Sea ECA.
To comply with these requirements, ships can use low-sulfur fuels, alternative fuels such as liquefied natural gas (LNG), or install exhaust gas cleaning systems (also known as scrubbers) that remove SOx emissions before they are released into the atmosphere.
Regulation 5: Volatile organic compounds (VOCs)
Regulation 5 of MARPOL Annex VI addresses the emissions of volatile organic compounds (VOCs) from ships. VOCs are organic chemicals that evaporate easily at room temperature and can contribute to air pollution, smog formation, and adverse health effects. In the context of shipping, VOC emissions are primarily associated with the loading, unloading, and storage of oil and chemical cargoes. This regulation requires ships with a capacity of 150 gross tons or more to develop and implement a VOC management plan to minimize VOC emissions from cargo tanks. The VOC management plan should outline the procedures and equipment used to control VOC emissions, such as vapor recovery systems, inert gas systems, and operational measures like minimizing cargo tank ullage and maintaining proper tank pressure. The plan must be approved by the ship’s flag state and is subject to inspection by port state control authorities. By implementing a VOC management plan, ships can reduce their environmental impact and contribute to improved air quality in ports and coastal areas.
Regulation 6: Shipboard incineration
Regulation 6 of MARPOL Annex VI aims to reduce air pollution caused by shipboard incineration. Incineration is a common method for disposing of waste materials onboard ships, but it can generate emissions that are harmful to the environment and human health, including particulate matter, sulfur oxides (SOx), nitrogen oxides (NOx), and toxic substances such as dioxins and furans. To minimize the environmental impact of shipboard incineration, this regulation restricts the types of materials that can be incinerated onboard and prohibits incineration in certain areas. The following materials are specifically prohibited from incineration:
- Annex I, II, and III cargo residues (oil, noxious liquid substances, and harmful substances in packaged form)
- Polychlorinated biphenyls (PCBs) and materials containing PCBs
- Garbage containing more than traces of heavy metals
- Refined petroleum products containing halogen compounds
- Sewage sludge and sludge oil
In addition, ships are prohibited from incinerating any materials while operating in ports, harbors, or estuaries, as well as in designated Emission Control Areas (ECAs) and other areas specified by the flag state or port state.
Incinerators installed on ships must be approved and certified to meet specific design and operational requirements, ensuring that they minimize harmful emissions and comply with the provisions of Annex VI.
Regulation 7: Reception facilities
Regulation 7 of MARPOL Annex VI emphasizes the importance of providing adequate reception facilities at ports for the proper disposal of ozone-depleting substances (ODS) and residues generated by exhaust gas cleaning systems (EGCS), also known as scrubbers. These reception facilities play a crucial role in preventing the illegal discharge of harmful substances into the environment, which can have detrimental effects on air and water quality as well as marine ecosystems. Under this regulation, port states are required to ensure the provision of adequate reception facilities for collecting, storing, and processing ODS and EGCS residues. These facilities must be capable of handling the types and quantities of residues generated by the ships visiting the port without causing undue delay. Port states are also responsible for notifying the International Maritime Organization (IMO) of the availability and capacity of their reception facilities, which is essential for monitoring and enforcing compliance with Annex VI requirements. To further support the implementation of this regulation, ships are required to offload their ODS and EGCS residues at designated reception facilities before leaving port. This helps ensure that harmful substances are properly managed and disposed of, contributing to a cleaner and more sustainable shipping industry.
Regulation 8: Port State control on operational requirements
Regulation 8 of MARPOL Annex VI establishes the framework for port state control (PSC) on the operational requirements of ships with regard to air pollution prevention. Port state control is a crucial mechanism for ensuring that foreign ships entering a port comply with international regulations, including those set forth in Annex VI.
Under this regulation, port state authorities are empowered to inspect foreign ships visiting their ports to verify their compliance with Annex VI requirements. Inspections may include the examination of relevant documentation, such as the ship’s International Air Pollution Prevention (IAPP) Certificate, Engine International Air Pollution Prevention (EIAPP) Certificate, Ozone-Depleting Substances Record Book, and Fuel Oil Non-Availability Report (FONAR), as well as the assessment of onboard equipment and operational practices.
If a ship is found to be in violation of Annex VI requirements, the port state may take enforcement actions, such as issuing a deficiency report, imposing fines or penalties, or detaining the ship until the identified issues are rectified. This ensures that ships operating in non-compliance with air pollution prevention regulations are held accountable for their actions, promoting a more responsible and environmentally friendly shipping industry.
Regulation 9: Requirements for platforms and drilling rigs
Regulation 9 of MARPOL Annex VI extends the scope of air pollution prevention measures to platforms and drilling rigs engaged in the exploration and exploitation of the seabed. These installations, which are often located offshore and can generate significant emissions, are subject to specific requirements under Annex VI to minimize their environmental impact.
Under this regulation, platforms and drilling rigs are required to comply with the same emissions standards for nitrogen oxides (NOx), sulfur oxides (SOx), and volatile organic compounds (VOCs) as applicable to ships under other Annex VI regulations. This includes adherence to the tiered NOx emission limits for diesel engines (Regulation 3), the sulfur content limits for fuel oil (Regulation 4), and the implementation of a VOC management plan (Regulation 5).
Additionally, platforms and drilling rigs must ensure that any shipboard incineration activities comply with the restrictions outlined in Regulation 6. These requirements collectively contribute to the reduction of air pollution from platforms and drilling rigs, helping to protect the environment and human health.
Regulation 10: Requirements for recreational craft
Regulation 10 of MARPOL Annex VI establishes emissions standards for recreational craft with a hull length of up to 24 meters. These vessels, which include motor yachts, sailing yachts, and other leisure boats, can contribute to air pollution and related environmental problems if not properly regulated.
Under this regulation, recreational craft are required to comply with specific emissions standards for nitrogen oxides (NOx) and carbon monoxide (CO) based on the engine’s power output. These standards apply to both gasoline and diesel engines installed on recreational craft, with the aim of reducing harmful emissions and promoting cleaner engine technologies.
Additionally, the regulation mandates that recreational craft be equipped with suitable devices or systems to prevent the discharge of untreated sewage into the water. This requirement helps to protect water quality and marine ecosystems from pollution caused by recreational boating activities.
By setting emissions standards for recreational craft, Regulation 10 of MARPOL Annex VI helps to ensure that the leisure boating sector contributes to a cleaner and more sustainable maritime environment.
Regulation 11: Energy efficiency for ships
Regulation 11 of MARPOL Annex VI focuses on enhancing the energy efficiency of ships, which plays a crucial role in reducing greenhouse gas (GHG) emissions and combating climate change. This regulation introduces two key mechanisms to achieve this goal: the Energy Efficiency Design Index (EEDI) and the Ship Energy Efficiency Management Plan (SEEMP).
The Energy Efficiency Design Index (EEDI) is a mandatory technical standard that sets minimum energy efficiency levels for new ships based on their size and type. It measures the amount of CO2 emitted per unit of transport work, taking into account factors such as ship size, capacity, speed, and installed power. The EEDI aims to stimulate innovation and the adoption of more energy-efficient technologies in the design and construction of new ships. Over time, the EEDI requirements become more stringent, pushing the industry towards increasingly efficient designs.
The Ship Energy Efficiency Management Plan (SEEMP) is a mandatory operational measure that requires each ship to have a documented plan for improving its energy efficiency. The SEEMP outlines the operational practices, procedures, and technologies that a ship will use to optimize its energy consumption and reduce GHG emissions. Examples of measures included in a SEEMP might be optimizing route planning, implementing speed reduction strategies, improving hull and propeller maintenance, and using energy-efficient lighting and equipment.
Together, the EEDI and SEEMP contribute to the overall goal of reducing the shipping industry’s carbon footprint and promoting more sustainable practices.
Regulation 12: Onboard monitoring and reporting of energy efficiency
Regulation 12 of MARPOL Annex VI addresses the monitoring and reporting of energy efficiency for ships of 5,000 gross tonnage and above. This regulation aims to enhance transparency and promote data-driven decision-making in the shipping industry, ultimately leading to more energy-efficient operations and reduced GHG emissions. Under this regulation, ships are required to collect and report data on their fuel consumption, distance traveled, and hours underway, as well as other relevant information that enables the calculation of the ship’s energy efficiency. This data is used to determine the ship’s annual average carbon intensity indicator (CII), which is then reported to the ship’s flag state and the International Maritime Organization (IMO). The flag state verifies the data and issues a Statement of Compliance (SOC) to confirm that the ship has met its monitoring and reporting obligations. The collected data is also used to develop a global database on ship energy efficiency, which informs policy-making and helps track the industry’s progress towards meeting its GHG emissions reduction targets. By implementing onboard monitoring and reporting requirements, Regulation 12 of MARPOL Annex VI helps to ensure that the shipping industry is held accountable for its energy efficiency and environmental performance.
Regulation 13: Nitrogen oxides (NOx) Tier III emission standards
Regulation 13 of MARPOL Annex VI establishes more stringent nitrogen oxide (NOx) emission standards for marine diesel engines installed on ships operating in designated NOx Emission Control Areas (NECAs). The Tier III emission standards aim to significantly reduce NOx emissions, which contribute to air pollution, smog, acid rain, and the eutrophication of water bodies, resulting in detrimental effects on human health and the environment.
The NOx Tier III emission standards apply to engines installed on ships constructed on or after January 1, 2016, when operating within a designated NECA. These standards require a reduction of NOx emissions by approximately 76.5% compared to the Tier I standards and 80% compared to the Tier II standards. This substantial reduction in emissions can be achieved through the use of advanced engine technologies, such as exhaust gas recirculation (EGR), selective catalytic reduction (SCR), and water-in-fuel emulsion (WIF) systems.
As of the end of 2022, there are four established NECAs: the Baltic Sea, the North Sea, the North American ECA, and the United States Caribbean Sea ECA. By implementing more stringent NOx emission standards within these areas, Regulation 13 contributes to the improvement of air quality and the protection of sensitive marine ecosystems.
Regulation 14: Reduction of sulfur oxide (SOx) emissions
Regulation 14 of MARPOL Annex VI focuses on reducing sulfur oxide (SOx) emissions from ships by introducing a global cap on the sulfur content of marine fuels and further lowering the sulfur limit in Emission Control Areas (ECAs). SOx emissions can cause respiratory issues, heart disease, and other health problems, as well as contribute to acid rain and the deterioration of ecosystems.
As of January 1, 2020, the global cap on the sulfur content of marine fuels has been reduced to 0.50% m/m (mass by mass), a significant decrease from the previous cap of 3.50% m/m. This reduction aims to significantly decrease the amount of SOx emissions from ships, leading to improved air quality and reduced health risks for coastal populations.
In designated ECAs, the sulfur content limit is even lower at 0.10% m/m, further reducing the environmental impact of shipping in these sensitive areas. The ECAs with stricter sulfur limits include the Baltic Sea, the North Sea, the North American ECA, and the United States Caribbean Sea ECA.
To comply with these limits, ships can use low-sulfur fuels, alternative fuels such as liquefied natural gas (LNG), or install exhaust gas cleaning systems (also known as scrubbers) that remove SOx emissions before they are released into the atmosphere. Through the implementation of Regulation 14, MARPOL Annex VI contributes to the reduction of air pollution and promotes a cleaner and more sustainable shipping industry.
Regulation 15: Fuel oil quality
Regulation 15 of MARPOL Annex VI focuses on ensuring that the fuel oil used onboard ships is safe and of acceptable quality. Proper fuel oil quality is essential for the efficient and environmentally responsible operation of ships, as low-quality fuels can cause engine problems, increase air pollution, and pose safety risks. Under this regulation, fuel oil suppliers must provide a “Bunker Delivery Note” (BDN) to the ship’s master or operator when supplying fuel. The BDN must include essential information about the fuel, such as its sulfur content, density, viscosity, and any other relevant characteristics. Furthermore, fuel oil must meet specific quality standards defined by the International Organization for Standardization (ISO), as specified in ISO 8217:2017 or later editions. Regulation 15 also prohibits the use of fuel oil with a sulfur content exceeding the limits set by Regulation 14, as well as the use of fuel oil that contains inorganic acid or used lubricating oil. By establishing strict fuel oil quality requirements, this regulation helps to ensure that ships operate safely and efficiently while minimizing their environmental impact.
Regulation 16: Verification procedures for a MARPOL Annex VI fuel oil sample
Regulation 16 of MARPOL Annex VI outlines the procedures for verifying the sulfur content of a representative fuel oil sample taken from a ship. This verification is essential for ensuring compliance with the sulfur content limits set by Regulation 14 and maintaining the integrity of the Emission Control Areas (ECAs). According to this regulation, the sulfur content of a fuel oil sample must be analyzed and verified by laboratories accredited by the flag state administration or a recognized organization. The analysis must be carried out using test methods specified by the International Organization for Standardization (ISO), such as ISO 8754:2003 or later editions. In the event of a dispute between the ship and the fuel oil supplier, the regulation outlines procedures for resolving the disagreement, which may include retesting the fuel oil sample at another accredited laboratory. By providing a clear framework for verifying fuel oil samples, Regulation 16 supports the enforcement of sulfur content limits and contributes to the overall goal of reducing air pollution from ships.
Regulation 17: Detection of violations and enforcement of the requirements
Regulation 17 of MARPOL Annex VI provides a framework for detecting violations of the annex’s requirements and enforcing its provisions. Ensuring compliance with Annex VI is crucial for achieving its objectives of reducing air pollution and promoting sustainable shipping practices.
Under this regulation, parties to the MARPOL Convention are required to establish appropriate sanctions for violations of Annex VI requirements. These sanctions may include fines, penalties, or the detention of non-compliant ships. Additionally, parties must cooperate in the detection of violations by sharing information and providing assistance to other parties when requested.
Regulation 17 also allows for port state control (PSC) inspections, as outlined in Regulation 8, to ensure that visiting foreign ships comply with Annex VI requirements. If a violation is detected during a PSC inspection, the port state may take enforcement actions, such as detaining the ship until the identified issues are rectified.
By providing a comprehensive framework for detecting violations and enforcing Annex VI requirements, Regulation 17 plays a vital role in ensuring the success of the annex’s pollution prevention measures and promoting a cleaner, more sustainable shipping industry.
Below is the summary of obligatory certificates and documents to be onboard ships according to MARPOL Annex VI:
| No. | Certificate / Document | Description |
|---|---|---|
| 1 | International Air Pollution Prevention (IAPP) Certificate | Confirms that the ship’s equipment and systems meet air pollution prevention standards after an initial or renewal survey. |
| 2 | Engine International Air Pollution Prevention (EIAPP) Certificate | Certifies that the marine diesel engine complies with the NOx emission limits set by MARPOL Annex VI. |
| 3 | Technical File | Contains relevant information about the engine, such as technical specifications, emission test results, and control measures. |
| 4 | Bunker Delivery Note (BDN) | Provided by the fuel oil supplier when bunkering and includes essential information about the fuel. Ships must retain BDNs for three years. |
| 5 | Fuel Oil Non-Availability Report (FONAR) | Submitted to the relevant authorities if a ship is unable to obtain compliant fuel oil, detailing efforts made and reasons for unavailability. |
| 6 | Ship Energy Efficiency Management Plan (SEEMP) | A documented plan for improving the ship’s energy efficiency, outlining operational practices, procedures, and technologies. |
| 7 | Energy Efficiency Design Index (EEDI) Technical File | Maintained onboard new ships, documenting the ship’s energy efficiency design and calculations. |
| 8 | Statement of Compliance (SOC) on the Monitoring, Reporting, and Verification (MRV) of CO2 emissions | Issued by the flag state administration or a recognized organization, confirming that the ship has met its MRV obligations. |
| 9 | Record Book of Engine Parameters (for ships with Tier III engines) | Logs relevant engine parameters, such as operational modes, emission control settings, and engine performance data. |
By Dr.Reza Karimpour